1. Field of the Invention
The invention relates to electronic detection and control. More specifically, it relates to the surveillance and control of aircraft and other vehicular movements on the runways, ramps and taxiways of an airport.
2. Description of the Prior Art
Airports in major metropolitan areas throughout the world handle large volumes of air traffic, resulting in well-known conditions of congestion, not only in the approach air space, but also on the surface of the airport itself. All types of aircraft making use of an airport have occasion to use runways for landing and takeoff and taxiways to and from these runways. In addition, various ramps and approach ways leading to maintenance and parking areas and to passenger and freight terminal areas are traversed bidirectionally by aircraft of all sizes. In addition to the ground movement of aircraft, trucks and other ground vehicles move about performing specialized tasks on the surface of the airport. Accordingly, a major airport requires some form of overall ground traffic control system. In order to be effective, such systems must be sensitive to a number of variables.
The prior art systems have relied primarily on visual observation and direct radio communication for navigation and control of aircraft and vehicles on the surface of the airport. Pilots and vehicle operators provide their own visual guidance and collision avoidance, while air traffic control personnel issue clearances and information as necessary to maintain safe, orderly and expeditious flow of surface traffic. Whenever air traffic personnel are unable to completely observe traffic on runways and taxiways, etc. (because of darkness, natural or man-made obstructions, precipitation, fog, etc.), the control of ground traffic must necessarily be based only on reports from pilots and vehicle operators. Under these conditions, traffic cannot be controlled in such a way that airport runways, taxiways and gates are utilized efficiently. The result is a considerable increase in pilot and controller workload, radio channel congestion, and operational delays.
Attempts have been made to provide radar coverage of the surface of an airport with high resolution surveillance radar sets operating in K-band and above. Such systems have been only partially successful however, because of inability to locate a reasonable number of such surveillance equipments to eliminate shadowing caused by various structures about the airport surface. Also, the higher radar frequencies used to give sufficient resolution were adversely affected by hydrometeroric phenomena over the relatively long distances involved on the surfaces of modern airports.
The basic requirements for an all weather surface guidance and control system to fill the general requirement can be stated as follows.
a. The system must provide aircraft and ground vehicles with information required for navigating within their movement areas during all weather conditions; this including the capability for locating and proceeding to a predetermined area or site anywhere on the airport surface.
b. The system must provide air traffic control personnel with information concerning the position of all aircraft and vehicles operating within the airport movement area and the relationship to each other as well as to runways, taxiways, intersections and fixed objects.
c. The system must provide an overall control arrangement adapted to be expanded from a basic location and path control system to a fully automatic routing system, ultimately with computer direction.
d. Additional equipment in aircraft and vehicles must be lightweight, compact and relatively inexpensive, as well as compatible with other equipment currently in use.
As aforementioned, visual and pilot reportage methods obviously cannot fulfil the aforementioned general requirements in all weather conditions. For reasons also given, the surface surveillance radars of the PPI type, or similar (usually employing the K-band), fall short of these requirements.
The manner in which the present invention provides solutions to the problems of the prior art, as discussed, and fulfills the general requirements recited, will be apparent as this description proceeds.